This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The effects of spaceflight on various physiological systems are clearly profound, and despite extensive research are incompletely understood. It is widely recognized, within both the space and scientific communities, that even short periods of exposure to microgravity can produce vestibular dysfunction, losses in muscle strength and function, and loss of orthostatic tolerance. Hence, there is a substantial amount of concern regarding the physiological deconditioning that might occur during longer duration spaceflights, for instance to Mars. Within this context, several countermeasures have been developed, but none appear to be completely effective. Therefore, a program priority of NASA's Biomedical Research and Countermeasures Program (NRA-03-OBPR-04) is to determine the potential usefulness of artificial gravity as a countermeasure, especially with respect to skeletal muscle atrophy and loss of muscle function. As Burton noted (15,16), the most obvious countermeasure to microgravity is a centrifuge, yet it has been the least explored. There are some obvious applications of artificial gravity as a countermeasure to microgravity. For instance, artificial gravity could be used to impose orthostatic challenges on the cardiovascular system, possibly preventing the loss of orthostatic tolerance that occurs as a result of microgravity. There are also some potential applications of artificial gravity in a microgravity environment that are not as obvious. As an example, artificial gravity/hypergravity in a microgravity environment could be used as a novel method of performing resistance training under high loading conditions.